The present invention relates to a side airbag apparatus that protects an occupant from an impact by deploying and inflating an airbag at a side of the occupant seated in a vehicle seat.
This kind of a side airbag apparatus includes an airbag and an inflator. The airbag is incorporated in a seatback of a car seat, together with the inflator, in a folded state. When an impact is applied to a side door or the like from a lateral direction, the inflator supplies inflation gas into the airbag. Accordingly, the airbag is projected from the car seat with a part of the airbag remaining in the seatback. The airbag is deployed and inflated forward from a narrow space between the occupant and a body-side portion. The airbag is located between the occupant and the body-side portion, which protrudes into the passenger compartment in a deployed and inflated state. As a result, the airbag restrains the occupant and buffers the impact that is transmitted from the side to the occupant.
The side airbag apparatus protects a region from a lumbar region to a thorax of the occupant. Further, it is known that the lumbar region of the occupant has higher impact resistance than the thorax. Therefore, it is preferable that the impact that acts on the thorax of the occupant be reduced more than the impact that acts on the lumbar region. Accordingly, there is proposed a side airbag apparatus that includes an upper-protecting-inflatable portion and a lower-protecting-inflatable portion, which are connected to each other via a communication passage, and a check valve, which is provided in the communication passage and restricts outflow of the inflation gas from the lower-protecting-inflatable portion to the upper-protecting-inflatable portion.
According to this configuration, more inflation gas is supplied to the lower-protecting-inflatable portion than to the upper-protecting-inflatable portion. In this case, the lower-protecting-inflatable portion, which is located near the lumbar region of the occupant, is deployed and inflated at an internal pressure higher than that of the upper-protecting-inflatable portion, which is located near the thorax of the occupant. The check valve restricts outflow of the inflation gas in the lower-protecting-inflatable portion to the upper-protecting-inflatable portion. Therefore, the internal pressure of the lower-protecting-inflatable portion is maintained in a high state. Further, a vent hole for releasing surplus inflation gas in the upper-protecting-inflatable portion to the outside of the airbag is provided in the upper-protecting-inflatable portion. Accordingly, the internal pressure of the upper-protecting-inflatable portion is adjusted at a proper value. In this way, each inflatable portion of the airbag is deployed and inflated at a suitable pressure according to the impact resistance of an occupant's side. Consequently, each of the lumbar region and the thorax of the occupant can be effectively protected from impact.
According to a side airbag apparatus described in Japanese Laid-Open Patent Publication No. 2004-262261, a partition portion is provided in an upper air chamber. A tubular air chamber that is curved to have a semi-annular shape is formed in the upper air chamber. According to this side airbag apparatus, the inflation gas supplied to the upper air chamber flows upward along the tubular air chamber, and subsequently flows downward. Therefore, the upper air chamber is sequentially deployed and inflated along an arm, a shoulder, and a temporal of the occupant. The impact resistance of an upper part of the upper body of the occupant is not uniform. For example, the impact resistance of the shoulder is higher than that of the thorax, and is lower than that of the lumbar region. Further, impact resistance of the rear half of the thorax is higher than that of the front half.
In this respect, according to Japanese Laid-Open Patent Publication No. 2004-262261, although the upper air chamber is deployed and inflated in a determined order, the internal pressure of the upper air chamber is uniform irrespective of each part. That is, a pressure distribution of the upper air chamber is not set by taking into account differences in impact resistances of parts of the upper body of the occupant. This fact is common to vehicles that are equipped with a side airbag apparatus, not only to cars.